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LXVII. On a brilliant Arch of an Aurora Borealis seen on 



the Evening of 'March 21, 1833. By R. Potter, Jun.Esq* 

 f\N this evening the sky was cloudy in the neighbourhood 

 ^^ of Manchester : it was nevertheless noticed by Mr. John 

 Blackwall, of Crumpsall Hall, by Mr. Hatfield, of Corn- 

 brook, and by myself, that there was a considerable light in 

 the N.N.W. ; no one in the neighbourhood, however, was 

 able to obtain a useful observation. 



This display was, however, seen in many other places situated 

 at considerable distances from each other, and the same ge- 

 neral description is given of it. Professor James D. Forbes 

 kindly sent me an account of his observation immediately after 

 it occurred ; and I am since also indebted to him for extracts 

 from the " Proceedings" of the Royal Society, giving particu- 

 lars of the observation of the Earl of Darnley, made at Athboy, 

 in Ireland. Having made a calculation of the height from 

 these observations, I drew up a short essay on the subject, 

 which was the first read in the Physical Section at the late 

 Meeting of the British Association at Cambridge-}-. Dr. Ro- 

 binson of Armagh, after the reading, mentioned his having 

 made an observation about the end of March, which, although 

 he had not then the date, might prove to be the same display, 

 and he politely offered me a copy of his notes. 



The following are extracts from the observations above 

 mentioned. Prof. Forbes, under the date of Edinburgh, 24th 

 of March 1833, writes: " Going out into the open air on the 

 evening of the 21st, at exactly 45 minutes past 8 m. t., I ob- 

 served a splendid luminous arch extending tolerably nearly 

 east and west, and considerably to the south of the zenith. It 

 perfectly resembled all the various displays of the phenome- 

 non which I have before seen, in its general character. But 

 in brilliancy it was probably exceeded by none ; not even, 

 I think, by that of the 19th of March 1825. As I was on my 

 way to witness some light-house experiments, I was unable to 

 make any precise observations; I obtained, however, such 

 data as will make the observation available for the determina- 

 tion of height. At 8 h 45 m the highest point of the arch passed 

 through the constellation of Leo, then about an hour from 

 the meridian. It also passed through a. Ononis, and, I think, 

 near Arcturus." " At its culminating point it occupied, as 

 nearly as I recollect, the space between y and £ Leonis ; its 

 breadth, therefore, was about 4°, but less towards the extre- 

 mities, where, as usual, it was most luminous. Its greatest 



* Communicated by the Author, 

 f See present vol. p. 152. — Edit. 



